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// Game_Music_Emu 0.5.5. http://www.slack.net/~ant/
#include "Fir_Resampler.h"
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
/* Copyright (C) 2004-2006 Shay Green. This module is free software; you
can redistribute it and/or modify it under the terms of the GNU Lesser
General Public License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version. This
module is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
details. You should have received a copy of the GNU Lesser General Public
License along with this module; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
#include "blargg_source.h"
#undef PI
#define PI 3.1415926535897932384626433832795029
static void gen_sinc( double rolloff, int width, double offset, double spacing, double scale,
int count, short* out )
{
double const maxh = 256;
double const step = PI / maxh * spacing;
double const to_w = maxh * 2 / width;
double const pow_a_n = pow( rolloff, maxh );
scale /= maxh * 2;
double angle = (count / 2 - 1 + offset) * -step;
while ( count-- )
{
*out++ = 0;
double w = angle * to_w;
if ( fabs( w ) < PI )
{
double rolloff_cos_a = rolloff * cos( angle );
double num = 1 - rolloff_cos_a -
pow_a_n * cos( maxh * angle ) +
pow_a_n * rolloff * cos( (maxh - 1) * angle );
double den = 1 - rolloff_cos_a - rolloff_cos_a + rolloff * rolloff;
double sinc = scale * num / den - scale;
out [-1] = (short) (cos( w ) * sinc + sinc);
}
angle += step;
}
}
Fir_Resampler_::Fir_Resampler_( int width, sample_t* impulses_ ) :
width_( width ),
write_offset( width * stereo - stereo ),
impulses( impulses_ )
{
write_pos = 0;
res = 1;
imp_phase = 0;
skip_bits = 0;
step = stereo;
ratio_ = 1.0;
}
Fir_Resampler_::~Fir_Resampler_() { }
void Fir_Resampler_::clear()
{
imp_phase = 0;
if ( buf.size() )
{
write_pos = &buf [write_offset];
memset( buf.begin(), 0, write_offset * sizeof buf [0] );
}
}
blargg_err_t Fir_Resampler_::buffer_size( int new_size )
{
RETURN_ERR( buf.resize( new_size + write_offset ) );
clear();
return 0;
}
double Fir_Resampler_::time_ratio( double new_factor, double rolloff, double gain )
{
ratio_ = new_factor;
double fstep = 0.0;
{
double least_error = 2;
double pos = 0;
res = -1;
for ( int r = 1; r <= max_res; r++ )
{
pos += ratio_;
double nearest = floor( pos + 0.5 );
double error = fabs( pos - nearest );
if ( error < least_error )
{
res = r;
fstep = nearest / res;
least_error = error;
}
}
}
skip_bits = 0;
step = stereo * (int) floor( fstep );
ratio_ = fstep;
fstep = fmod( fstep, 1.0 );
double filter = (ratio_ < 1.0) ? 1.0 : 1.0 / ratio_;
double pos = 0.0;
input_per_cycle = 0;
for ( int i = 0; i < res; i++ )
{
gen_sinc( rolloff, int (width_ * filter + 1) & ~1, pos, filter,
double (0x7FFF * gain * filter),
(int) width_, impulses + i * width_ );
pos += fstep;
input_per_cycle += step;
if ( pos >= 0.9999999 )
{
pos -= 1.0;
skip_bits |= 1 << i;
input_per_cycle++;
}
}
clear();
return ratio_;
}
int Fir_Resampler_::input_needed( blargg_long output_count ) const
{
blargg_long input_count = 0;
unsigned long skip = skip_bits >> imp_phase;
int remain = res - imp_phase;
while ( (output_count -= 2) > 0 )
{
input_count += step + (skip & 1) * stereo;
skip >>= 1;
if ( !--remain )
{
skip = skip_bits;
remain = res;
}
output_count -= 2;
}
long input_extra = input_count - (write_pos - &buf [(width_ - 1) * stereo]);
if ( input_extra < 0 )
input_extra = 0;
return input_extra;
}
int Fir_Resampler_::avail_( blargg_long input_count ) const
{
int cycle_count = input_count / input_per_cycle;
int output_count = cycle_count * res * stereo;
input_count -= cycle_count * input_per_cycle;
blargg_ulong skip = skip_bits >> imp_phase;
int remain = res - imp_phase;
while ( input_count >= 0 )
{
input_count -= step + (skip & 1) * stereo;
skip >>= 1;
if ( !--remain )
{
skip = skip_bits;
remain = res;
}
output_count += 2;
}
return output_count;
}
int Fir_Resampler_::skip_input( long count )
{
int remain = write_pos - buf.begin();
int max_count = remain - width_ * stereo;
if ( count > max_count )
count = max_count;
remain -= count;
write_pos = &buf [remain];
memmove( buf.begin(), &buf [count], remain * sizeof buf [0] );
return count;
}
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